Electrical vacuum pump



8, 1936 c. w. HANsELL ELECTRICAL VACUUM PUK? original Filed DeG. 14, 1.932

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C AC M0701? /V :NVENTOR /Zz #A605727 CLARENCE W ANSELL BY? /wPi/ f ToRNEY Patented Dec. 8,- 1936 ELECTRICAL VACUUM PUMP Clarence W. Hansell, Port Jefferson, N. Y., assignor to Radio Corporation of America, a, corporation, of Delaware Original application December 14, 1932, Serial No. 647,189. Divided and this application September 29, 1934, Serial No. 746,060

6 Claims.

This invention is a division of my United States Patent No. 2,022,465, granted November 26, 1925, and relates to apparatus for producing high vacua in closed receptacles, such as bulbs, electron discharge devices and the like, and has for its object to provide a simplied and improved type of vacuum pump.

In present day evacuation processes it is customary to use some form of rotating or reciprocating mechanical pump sealed with oil for producing an initial or rough vacuum. In manuiacturing electron discharge devices for receiving purposes, the final evacuation pumping is ordinarily accomplished by means of a getter inside the device, which, when heated, will absorb gases by chemical reaction. In the case of electron discharge devices for transmitting purposes, the usual method of producing the iinal vacuum is to employ a Langmuir mercury vapor condensation pump o the type described in United States Patent No. 1,393,550, granted October 11, 1921 to I. Langmuir, which is operated in series with a mechanical pump. It is common practice, in both of these cases, to heat up the ele; ments of the discharge device during the evacuation process for the purpose of driving out occluded gases from the parts of the vacuum tube. Although these methods are successful they require parts which are expensive and diflicult to construct, with the result that they do not lend themselves readily to construction and operation by amateurs or to use in small laboratories. The present invention, however, by its simplicity of construction overcomes these difficulties and enables its use by amateurs, besides providing for obtaining faster evacuation and higher vacua. Another advantage of the present invention is that it is readily adaptable to large scale production of vacuum devices 'with the aid of automatic machines.

More specifically, the present invention comprises a, vacuum pump wherein electrical forces are utilized for effecting the evacuation process. This is accomplished by producing a direct current discharge through a tube or oriilce between a. vessel to be exhausted and the inlet to the rough pump, the discharge consisting chieiiy of a iiow of electrons in one direction and a flow of gas ions and molecules in the other direction. This flow of ions continues until the vessel is exhausted. To initiate the discharge and make starting easier there may be used a hot cathode and a relatively low voltage supply. If desired, however, there may be used relatively cold electrodes, the arc between them being established -vention for effecting an improvement in the (Cl. 23o-69) by the momentary application of very high voltages to directly ionize the gas in the discharge path.

' Although the present invention will be hereinafter described with special regard to vacuum pumps, it should be distinctly understood that it is not limited thereto since the principles thereof may be used for producing pressure as well as obtaining a vacuum.

The following is a detailed description, accom- 10 panied by a drawing, wherein the single gure illustrates one embodiment of the invention.

The system of the drawing shows one way in which to apply the principles of the present in- Langmuir mercury condensation pump previously referred to. In this drawing, there is shown a bulb II containing a filament I2 and a pool of mercury I 3 through which an electric discharge may be considered to take place in the same manner as in the well known hot cathode mercury vapor rectifier tube. The presence of this electrical discharge causes ions of mercury to exist within the bulb I I, which are drawn toward the electrode I2, to which there is applied a negative potential from a direct current generator 10. The vessel to be exhausted 9 is shown connected by tubing 8 to an inlet passage I4 which, together with an orifice 39, extending from tube I I to the inlet, connects with a condensing chamber I5.

This condensing chamber is arranged to be' y cooled by a fluid circulating in vessel 30, the cooling fluid being conducted into the vessel 30 by means of pipe I6 and withdrawn by suction on the pipe I'I. A rough vacuum pump'2 connects with the condensing chamber through a passage or inlet I8.

In the operation of the device, the heating of the mercury in the chamber II, due to the electrical discharge in it, will build up a mercury vapor pressure While the cooling inside the vessel 30 causes it to have a much lower pressure. Consequently, a blast of mercury vapor will issue from the orifice 39. The presence of an electrical discharge will cause ions of mercury to exist within bulb II which, when drawn toward electrode 28 by the application of the negative potential thereto, will greatly increase the force of the blast of mercury ions in the orice 39, which corresponds to the orice in the Langmuir pump. The blast of ions and mercury molecules will trap and carry out molecules of gas from the inlet or conduit I4 connected to the vessel 9 to be evacuated. v".lhe ions passing through the orifice of the pump are neutralized when they come in contact with the electrode Il and then pass as neutral mercury vapor into condensing chamber cooling from the cooling liquid circulated in vessel 30 around the chamber. 'Ihe condensed mercury is caused to fall by gravity into a tube Il which returns the mercury to the bulb Il. At the return end of the condensing chamber Il there is shown the rough exhaust pump 2. By connecting the metal elements in the vessel l to a source of positive potential as indicated. the tendency for any mercury vapor to 'diil'use back into the vessel 9 will be reduced. A very low temperature may also be applied, by means of cooling fluids as shown in the drawing, to the tube I4 in the final states of pumping to accomplish the same purpose.

por into the rough pump.

Suitable circuits are shown, schematically, in a well known manner, for maintaining the electrical potentialsand current discharges in the various parts'of the pump.

If desired, the lament of the mercury bulb i I may be omitted. 'In such case. the arc will be established between relatively cold electrodes and the apparatus is just as effective for producing the pumping action as when a heated lament is used for the negative electrode. The main reason for using filaments is to make the starting of the arc discharge easier, but this starting could also be accomplished by momentarily applying a high voltage suillcient to directly ionize the gas in the discharge path and start an arc. Another manner of starting an arc is to bring into the vicinity of the discharge path the point oi a Tesla coil which will set up very high potentials around it and which will cause a breakdown of the gas.

It should be distinctly understood that the present invention ls not limited to the precise arrangements and design features shown since these have merely been illustrated for the purpose of setting forth clearly the principles of the present invention. The proportions and dimensions of parts may, and undoubtedly will, be altered to obtain optimum operation with different designs.

What is claimed is:

1. An apparatus for exhausting closed receptacles comprising means for producing a stream of gas ions, a condensing chamber, a conduit through which the stream of gas ions flows to the condensing chamber, a second conduit communicating with the receptacle which is to be exhausted and with the first conduit, and means for neutralizing and means for cooling said stream of gas ions.

2. Apparatus for obtaining a high vacuum in a closed receptacle comprising a hot cathode mercury vapor rectifier having a filament and a source of supply for heating said filament whereby an electrical discharge takes place for producing a stream of mercury gas ions, a conil where they are condensed by- Likewise, the tube Il mayv `be cooled to reduce the diffusion of mercury vadensing chamber, a conduit at one end ot the condensing chamber through which the stream of mercury gas ions flows to the condensing chamber, a second conduit communicating with the receptacle which is to be exhausted and with the nrst conduit, a rough pump at the other end oi said chamber, and cooling means for preventing said mercury gas ions from flowing from the first conduit through the second conduit towards the receptacle which is to be exhausted.

3. Apparatus for obtaining a high vacuum in a closed receptacle comprising a hot cathode mercury vapor rectifier having a lament and a source o! supply for heating said filament whereby an electrical discharge takes place for producing a stream of mercury gas ions, a condensing chamber, a conduit at one end of the condensing chamber through which the stream of mercury gas ions chamber, a second conduit communicating with the receptacle which is to be exhausted and with the first conduit, a rough pump at the other end cooling means for preventing said mercury gas ions from nowing from the first conduit through the second conduit towards turning same to said mercury vapor rectier.

4. An apparatus for exhausting closed receptacles comprising means including a vapor rectiiler for producing a stream of gas ions, a' condensing chamber, a conduit through which the stream of gas ions flows to the condensing chamber, a second conduit communicating with the receptacle which is to be exhausted and with the first conduit, means for neutralizing and means for cooling said stream of gas ions, and a path for collecting the neutralized and cooled gas ions and returning same to said vapor rectiner.

5. Apparatus for obtaining a high vacuum in a closed receptacle comprising ineens` for producing a stream of mercury gas ions, a condensing chamber, a conduit through which the stream of mercury gas ions ows to the condensing chamber, a second conduit communicating with the receptacle which is to be exhausted and with the first conduit, and cooling means for preventing said mercury gas ions from flowing from the first conduit through the second conduit towards the receptacle which is to be exhausted.

6. Apparatus for obtaining a high vacuum in a closed receptacle containing metal elements, comprising means for producing a stream of gas ions, a chamber communicating with a rough pump, a conduit through which the stream of gas ions flows to said chamber, a second conduit communicating with the receptacle which is to be exhausted and with the iirst conduit, and means for reducing the tendency of said gas ions to diffuse back into said receptacle including a source of potential and a connection from the positive terminal of said source to said metal elements.

CLARENCE W. HANSELL.

flows to the condensing" 

